U.S. patent number 5,749,626 [Application Number 08/859,114] was granted by the patent office on 1998-05-12 for rotary-cam type reclining device.
This patent grant is currently assigned to Ikeda Bussan Co., Ltd.. Invention is credited to Tomonori Yoshida.
United States Patent |
5,749,626 |
Yoshida |
May 12, 1998 |
Rotary-cam type reclining device
Abstract
A reclining device comprises a stationary base fixedly connected
to a seat cushion, a pivotal, press-worked arm fixedly connected to
a seat back and rotatably supported on the base and having an inner
toothed portion, at least one toothed block slidably disposed
between the base and the arm and having an outer toothed portion
meshable with the inner toothed portion, and a rotary cam in
cam-connection with the toothed block for producing an outward or
inward sliding motion of the toothed block to mesh or unmesh the
outer toothed portion with or from the inner toothed portion by
rotation of the cam. To balance two contradictory requirements,
that is reduction of undue sink mark (lack of fill) and high
mechanical strength (high durability), a reinforced portion of a
lack-of-fill suppressive geometry and shape, being composed of at
least two outside curved faces, is integrally formed with the arm
all around the circumferentially-extending stepped portion on an
arm outside face opposed to an arm inside face formed with the
inner toothed portion.
Inventors: |
Yoshida; Tomonori (Yokohama,
JP) |
Assignee: |
Ikeda Bussan Co., Ltd. (Ayase,
JP)
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Family
ID: |
15491738 |
Appl.
No.: |
08/859,114 |
Filed: |
May 20, 1997 |
Foreign Application Priority Data
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May 22, 1996 [JP] |
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8-150201 |
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Current U.S.
Class: |
297/367R;
297/362; 74/438 |
Current CPC
Class: |
B60N
2/236 (20150401); Y10T 74/19888 (20150115) |
Current International
Class: |
B60N
2/235 (20060101); B60N 002/22 (); B21K
001/30 () |
Field of
Search: |
;297/362,367,463.2
;74/438,462 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 756 961 |
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Feb 1997 |
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EP |
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6-125821 |
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May 1994 |
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JP |
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Primary Examiner: Brown; Peter R.
Attorney, Agent or Firm: Foley & Lardner
Claims
What is claimed is:
1. A reclining device, comprising:
a stationary base (1) adapted to be fixedly connected to a seat
cushion (32);
a pivotable, press-worked arm (2) adapted to be fixedly connected
to a seat back (33) and pivotally supported on said base by a pivot
shaft (4), said arm (2) formed integral with a recessed portion
(19) having an inner toothed portion (21a; 21b) on an inner
peripheral wall thereof;
a toothed block (12A; 12B) slidably disposed between said base (1)
and said arm (2) and having an outer toothed portion (13) on an
outer periphery thereof;
said base (1) being formed integral with a recessed guide (10)
having guiding side walls for slidably guiding said toothed block
(12A; 12B) outwardly away from a center of rotation of said arm or
inwardly towards the center of rotation of said arm;
a rotary cam (16) in cam-connection with said toothed block (12A;
12B) for producing an outward sliding motion of said toothed block
to mesh said outer toothed portion (13) with said inner toothed
portion (21a; 21b) by a rotary motion of said cam in a first
rotational direction and for producing an inward sliding motion of
said toothed block to unmesh said outer toothed portion (13) from
said inner toothed portion (21a; 21b) by a rotary motion of said
cam in a second rotational direction opposing said first rotational
direction; and
an operating lever (3) mechanically linked to said cam for
producing said rotary motion of said cam;
wherein a thick-walled reinforced portion (24) of a lack-of-fill
suppressive geometry and shape, being composed of at least two
outside curved faces, is integrally formed with said arm all around
a circumferentially-extending stepped portion (22) on an arm
outside face opposed to an arm inside face formed with said inner
toothed portion (21a; 21b).
2. A reclining device as claimed in claim 1, wherein a part of said
thick-walled reinforced portion (24) of said lack-of-fill
suppressive geometry and shape, is formed integral with a stronger
reinforced portion (25) of an essentially rectangular equilateral
triangle in cross-section, whose base angles are 45 degrees or
less.
3. A reclining device as claimed in claim 2, wherein a plurality of
stronger reinforced portions (25) are formed integral with said
thick-walled reinforced portion (24) of the lack-of-fill
suppressive geometry and shape, circumferentially equi-distantly at
predetermined angular positions.
4. A reclining device as claimed in claim 1, wherein said
thick-walled reinforced portion (24) of said lack-of-fill
suppressive geometry and shape, is integrally formed with said arm
by press-working.
5. A reclining device as claimed in claim 1, wherein said
thick-walled reinforced portion (24) of said lack-of-fill
suppressive geometry and shape, is integrally formed with said arm
by cold-forging.
6. A reclining device as claimed in claim 1, wherein said at least
two outside curved faces comprise a first curved concave surface
(F.sub.1) composed of a part of circle of curvature with a first
radius (R.sub.1) and a center of curvature located outside of the
arm outside face opposite to the arm inside face formed with said
inner toothed portion (21a; 21b), a second curved convex surface
(F.sub.2) composed of a part of circle of curvature with a second
radius (R.sub.2) greater than said first radius and a center of
curvature located inside of the arm inside face, and a third curved
concave surface (F.sub.3) composed of a part of circle of curvature
with a third radius (R.sub.3) greater than said first radius
(R.sub.1) and less than the second radius (R.sub.2) and a center of
curvature located outside of the arm outside face.
7. A reclining device as claimed in claim 6, wherein a thickness of
said thick-walled reinforced portion (24), measured in an axial
direction of said pivot shaft (4) is 1/5 or less the sum of a
thickness of said inner toothed portion (21a; 21b) and a thickness
of a thin-walled section (23) of said circumferentially-extending
stepped portion (22).
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rotary-cam type reclining device
which is locked or unlocked by way of a rotary motion of a rotary
cam mechanically linked to a reclining lever for adjusting the
angular position of a seat back relative to an associated seat
cushion to provide the seat occupant to the desired seat-back
inclination.
2. Description of the Prior Art
In recent years, there have been proposed and developed various
rotary-cam type reclining devices. One such rotary-cam type
reclining device has been disclosed in Japanese Patent Provisional
Publication No. 6-125821 (corresponding to French Patent
Application No. 91 02590 filed on Mar. 5, 1991). A reclining device
disclosed in the Japanese Patent Provisional Publication No.
6-125821 includes a stationary flange portion (called a base)
fixedly connected to a seat cushion, a rotatable or pivotable
flange portion (called an arm) fixedly connected to a seat back,
and a rotary cam. The rotatable flange portion (the arm) is formed
with an inner toothed portion on its inner periphery. The
stationary flange portion is formed with a plurality of cup-like
recessed portions, each radially guiding and slidably accommodating
therein a toothed block. A plurality of block pushers are
interposed the rotary cam and the respective toothed blocks. Each
toothed block, often called "tooth inner", can be meshed with or
unmeshed from the inner toothed portion of the arm by rotation of
the rotary cam. In case of such rotary-cam type reclining devices,
the locked state of the reclining device is kept by way of
meshed-engagement between the toothed block and the inner toothed
portion of the arm. Thus, it is desired to assure an increased
mechanical strength of the inner toothed section of the arm. On the
contrary, it is desirable to thin the thickness of the arm as much
as possible in order to satisfy the requirement for light-weighting
of component parts such as a pivotable arm and a stationary base.
To balance these two contradictory requirements, that is
light-weight and high mechanical strength (high durability), a
thick-walled reinforced portion is often provided near the inner
toothed portion of the arm. FIG. 7 shows a partial cross section of
a pivotal arm of a prior art reclining device having the
previously-discussed thick-walled reinforced portion. As seen in
FIG. 7, in case of the prior art arm structure, a reinforced
portion 53 of an essentially rectangular equilateral triangle (base
angles are 45 degrees) in cross section, is conventionally provided
at the circumferentially-extending stepped portion 52 nearing the
inner toothed portion 51 of the arm member 50 so that the
reinforced portion 53 is formed on one face of the arm opposed to
the other face formed with the inner toothed portion 51.
Ordinarily, to reduce production costs of the reclining device
assembly, the reinforced portion 53 of the rectangular equilateral
triangle in cross section is integrally formed with the arm member
50 all over the circumferentially-extending stepped portion 52 by
way of press-working such as cold-forging. As is generally known,
such press-working for example cold-forging results in lack of
metal fill due to elastic deformation which can occur after
press-working. In FIGS. 7, three sections denoted by H.sub.1,
H.sub.2 and H.sub.3 correspond to lack of metal fill. Such lack of
fill (or shrinkage) is often called as a "sink mark". In case that
the reinforced portion 53 (of the rectangular equilateral triangle
in cross section) is continuously formed integral with the arm
member all around the circumferentially-extending stepped portion
52, there is a tendency for the amount of metal allotted to the
reinforced portion 53 to increase. The increased amount of metal
allotted to the reinforced portion 53 tends to increase sink marks
in some locations, namely the lack of fill H.sub.1 at each edge of
teeth of the inner toothed portion 51, the lack of fill H.sub.2 at
each corner of teeth of the inner toothed portion 51 and the lack
of fill H.sub.3 at each edge nearing the reinforced portion 53.
Typically, the arm member 50 has a non-toothed portion in addition
to an inner toothed portion 51 partly formed only within
predetermined angular ranges. As may be appreciated, the sink mark
H tends to be remarkably increased at a section having the inner
toothed portion 51, owing to the increased amount of metal allotted
to the reinforced portion 53 and also owing to a number of teeth
constructing the inner toothed portion 51. This reduces a
mechanical strength during meshed-engagement between the inner
toothed portion 51 and the toothed block. The increased sink mark H
causes the toothed block to be partly unmeshed from the inner
toothed portion 51.
To avoid this, the reinforced portion of an essentially rectangular
equilateral triangle in cross section is often formed integral with
the arm member partly (intermittently) and circumferentially
equi-distantly at predetermined angular positions. In case of the
partial reinforcement, the number of reinforced points must be
increased to provide adequate rigidity of the
circumferentially-extending stepped portion of the arm member. This
increases the difficulty of press-working to the arm member with
the inner toothed portion and the reinforcement composed of a large
number of reinforced portions formed circumferentially and
equi-distantly along the stepped portion of the arm member. As seen
in FIG. 8, the wall thickness of the stepped portion is
comparatively thinned within a non-reinforced section between the
two adjacent partly-reinforced portions. The prior art reclining
device suffers from the additional drawback that cracks J (such as
shear fracture) may occur at the non-reinforced sections owing to
fatigue caused by repeated shearing force imparted thereto.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a
rotary-cam type reclining device which avoids the aforementioned
disadvantages of the prior art.
It is another object of the invention to provide a rotary-cam type
reclining device, which is capable of balancing two contradictory
requirements, that is, suppression of undesired sink mark and high
rigidity of the pivotable arm member with an inner toothed portion,
irrespective of utilizing a metal material having the same
thickness as an arm member employed in the prior art rotary-cam
type reclining device.
Briefly speaking, a rotary-cam type reclining device made according
to the present invention is featured by a somewhat thick-walled
reinforcement of a specified sink-mark suppressive shape or
cross-section, which reinforcement is formed all around the
circumferentially-extending stepped portion nearing the inner
toothed portion of the pivotable arm member.
In order to accomplish the aforementioned and other objects of the
present invention, a reclining device, comprises a stationary base
adapted to be fixedly connected to a seat cushion, a pivotable,
press-worked arm adapted to be fixedly connected to a seat back and
pivotally supported on the base by a pivot shaft, the arm formed
integral with a recessed portion having an inner toothed portion on
an inner peripheral wall thereof, a toothed block slidably disposed
between the base and the arm and having an outer toothed portion on
an outer periphery thereof, the base being formed integral with a
recessed guide having guiding side walls for slidably guiding the
toothed block outwardly away from a center of rotation of the arm
or inwardly towards the center of rotation of the arm, a rotary cam
in cam-connection with the toothed block for producing an outward
sliding motion of the toothed block to mesh the outer toothed
portion with the inner toothed portion by a rotary motion of the
cam in a first rotational direction and for producing an inward
sliding motion of the toothed block to unmesh the outer toothed
portion from the inner toothed portion by a rotary motion of the
cam in a second rotational direction opposing the first rotational
direction, and an operating lever mechanically linked to the cam
for producing the rotary motion of the cam, wherein a thick-walled
reinforced portion of a lack-of-fill suppressive geometry and
shape, being composed of at least two outside curved faces, is
integrally formed with the arm all around a
circumferentially-extending stepped portion on an arm outside face
opposed to an arm inside face formed with the inner toothed
portion. A part of the thick-walled reinforced portion of the
lack-of-fill suppressive geometry and shape, may be formed integral
with a stronger reinforced portion of an essentially rectangular
equilateral triangle in cross-section, whose base angles are 45
degrees or less. The thick-walled reinforced portion of the
lack-of-fill suppressive geometry and shape, is integrally formed
with the arm by press-working, preferably cold-forging. The at
least two outside curved faces may comprise a first curved concave
surface composed of a part of circle of curvature with a first
radius and a center of curvature located outside of the arm outside
face opposite to the arm inside face formed with the inner toothed
portion, a second curved convex surface composed of a part of
circle of curvature with a second radius greater than the first
radius and a center of curvature located inside of the arm inside
face, and a third curved concave surface composed of a part of
circle of curvature with a third radius greater than the first
radius and less than the second radius and a center of curvature
located outside of the arm outside face. It is preferable that a
thickness of the thick-walled reinforced portion, measured in an
axial direction of the pivot shaft is 1/5 or less the sum of a
thickness of the inner toothed portion and a thickness of a
thin-walled section of the circumferentially-extending stepped
portion. It is preferable that a plurality of stronger reinforced
portions are formed integral with the reinforced portion of the
lack-of-fill suppressive geometry and shape, circumferentially
equi-distantly at predetermined angular positions.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view illustrating one embodiment of a
rotary-cam type reclining device made according to the
invention.
FIG. 2 is a side elevation view illustrating the reclining device
of the embodiment shown in FIG. 1.
FIG. 3 is a cross-sectional view taken along the line A--A of FIG.
2.
FIG. 4 is a dis-assembled view of the reclining device of the
embodiment shown in FIG. 1.
FIG. 5A is an enlarged partial cross-sectional view illustrating a
somewhat thick-walled reinforced portion formed near the inner
toothed portion of a pivotable arm member employed in the device of
the embodiment and having a specified sink-mark suppressive
cross-section.
FIG. 5B is an enlarged partial cross-sectional view illustrating a
partial strongly-reinforced portion having an essentially
rectangular equilateral triangle (base angle being 45 degrees or
less) in cross section.
FIG. 6A is a side view showing a completely-locked state of the
reclining device of the embodiment.
FIG. 6B is an illustration of a statical analysis of the components
of a force applied to the toothed block and to the arm member due
to the arm loaded in the clockwise direction.
FIG. 7 is an enlarged partial cross-sectional view illustrating a
thick-walled reinforced portion formed near the inner toothed
portion of a pivotable arm member employed in the prior art
reclining device.
FIG. 8 is an enlarged partial cross-sectional view illustrating a
non-reinforced portion of the arm member employed in the prior art
reclining device.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, particularly to FIGS. 1, 2 and 3,
the rotary-cam type reclining device of the invention is applied to
a double-sided reclining apparatus in which a pair of pivotal arms
2A and 2B (which will be represented by reference sign 2 as
generally referred to) are rotatably or pivotably supported on the
respective stationary bases 1A and 1B (which will be represented by
reference sign 1 as generally referred to) through pivot shafts 4A
and 4B (which will be represented by reference sign 4) being
mechanically linked to each other by means of a connecting pipe 29.
Actually, the connecting pipe 29 is fixedly connected to both the
innermost ends of the pivot shafts 4A and 4B by means of serration
connection, spline connection or the like. As seen in FIG. 2, a
reclining lever (or an operating lever) 3 is fixedly connected to
the pivot shaft 4B. As appreciated from FIG. 1, a pair of reclining
devices are symmetrically arranged with respect to the center line
of the seat assembly. As appreciated from FIGS. 1 to 4, the
construction of the left-hand reclining device is essentially
similar to that of the right-hand reclining device except that only
the right-hand reclining device employs the reclining lever 3. As
shown in FIGS. 1 to 4, each of the bases 1A and 1B is formed with
mounting-bolt holes 6a and 6b through which the associated
stationary base is fixedly connected to a frame of a seat cushion
32 by means of bolts or the like. Each of the pivotal arms 2A and
2B is fixedly connected to a seat back 33 through mounting-bolt
holes 18a and 18b by means of bolts or the like. As seen in FIGS. 3
and 4, the base 1 is formed with an essentially circular recessed
portion 8. The base 1 (1A; 1B) has a central bore 7 in its circular
recessed portion 8, the arm 2 (2A; 2B) has a central bore 20, and
the rotary cam 16 has a substantially rectangular central bore (not
numbered). The pivot shaft 4 of the reclining lever is rotatably
fitted to the central bore 7 of the base through the central bore
20 of the arm and the substantially rectangular central bore (not
numbered) of the rotary cam 16. As seen in FIGS. 1, 3 and 4, the
recessed portion 8 of the base 1 has a substantially rectangular
vertically-extending bottom wall portion 8a (having the central
bore 7) and a substantially rectangular recessed portion 10 further
recessed from the bottom wall portion 8a. The recessed portion 10
is defined by a pair of diametrically-opposing elongated,
rotary-cam guiding side walls 9a and 9b, an upper circular-arc
shaped side wall 9c bridging the gap between uppermost ends of the
two side walls 9a and 9b, and a lower circular-arc shaped side wall
9d bridging the gap between lowermost ends of the two side walls 9a
and 9b. As best seen in FIG. 3, the upper circular-arc shaped side
wall 9c is formed with a curved inner toothed portion 11a, while
the lower circular-arc shaped side wall 9d is formed with a curved
inner toothed portion 11b. The toothed portions 11a and 11b are
brought into meshed-engagement with respective outer toothed
portions 13 of upper and lower toothed blocks 12A and 12B which
will be fully described in detail. As seen in FIGS. 3 and 4, a pair
of toothed blocks 12A and 12B are operably accommodated in the
recessed portion 10 of the base in such a manner as to be slidable
radially with respect to the pivot shaft, while being guided by the
guiding side walls 9a and 9b. As best seen in FIG. 4, each of the
toothed blocks 12A and 12B has the outer toothed portion 13 and a
cam-contour surface 14 on its inner periphery. As best seen in
FIGS. 4 and 6A, the respective cam-contour surfaces (14; 14) of the
toothed blocks 12A and 12B are point-symmetrical with respect to
the axis of the central bore 7 of the base. Each cam-contour
surface 14 comprises a pair of substantially 45.degree.-sloped
cam-connection portions 14a and 14b formed at both ends of the
inner peripheral wall surface of the respective toothed block (12A;
12B), a curved portion 14c curved from the 45.degree.-sloped
cam-connection portion 14a in the clockwise direction, a
substantially straight cam-connection portion 14d horizontally
extending from the innermost end of the curved portion 14c, and a
curved groove-cut portion 14e being continuous with the
45.degree.-sloped cam-connection portion 14b and the substantially
straight horizontally-extending cam-connection portion 14d. On the
other hand, the rotary cam 16 is formed with a pair of
diametrically-opposing cam-profile surfaces on its outer periphery.
As best seen in FIG. 6A, each of the pair of cam-profile surfaces
of the rotary cam 16 comprises two slightly-raised cam portions 16a
and 16b being abuttable with the respective cam-connection portions
14a and 14b, a moderately-curved cam portion 16c curved from the
slightly-raised cam portion 16a in the clockwise direction, an
essentially-straight cam portion 16d being continuous with the
curved cam portion 16c, a finger-tip like cam portion 16e extending
clockwise from the cam portion 16d and a slightly undulated
groove-cut portion 16f defined between the finger-tip like cam
portion 16e and the raised cam portion 16b. As seen in FIG. 4, the
pivot shaft 4 has a pair of diametrically-opposing circular-arc
faces and a pair of rectangular flat faces. Each circular arc-face
serves as a sliding surface which is slidably fitted to the inner
peripheral surface of the central bore 20 of the arm. For
co-rotation with the pivot shaft 4 of the operating lever 3, the
substantially-rectangular bore of the rotary cam 16 is contoured in
a manner so as to be precisely fitted onto the pivot shaft 4
without any play. After the pivot shaft 4 is fitted into the bore 7
of the base 1 while supporting thereon the arm 2 and the rotary cam
16, a snap ring 27 is fitted on the free end of the pivot shaft 4
to prevent the axial movement of the pivot shaft 4 relative to the
base 1. The arm 2 is formed integral with an essentially
cylindrical ring-gear like recessed portion 19 having the same
radius as the two circular-arc shaped side walls 9c and 9d
diametrically opposed to each other. The ring-gear like recessed
portion 19 is formed with a pair of inner toothed portions 21a and
21b on its inner peripheral wall surface such that these toothed
portions 21a (the center of the upper toothed portion 21a being
slightly angularly counter-clockwise offset from the uppermost end
of the ring-like recessed portion 19 in FIG. 6A) and 21b (the
center of the lower toothed portion 21b being slightly angularly
counter-clockwise offset from the lowermost end of the ring-like
recessed portion 19 in FIG. 6A) are diametrically opposite to each
other within a predetermined angular range such as 120 degrees. As
seen in FIG. 6A, the two inner toothed portions 21a and 21b of the
arm are point-symmetrical with respect to the axis of the pivot
shaft 4. When assembling, the pair of upper and lower toothed
blocks 12A and 12B are operably accommodated in an internal space
defined between the ring-gear like recessed portion 19 of the arm 2
and the substantially rectangular recessed portion 10 of the base
1, so that the outer toothed portion 13 of each toothed block (12A;
12B) is meshable with and unmeshable from the associated inner
toothed portion (21a; 21b) of the arm 2, and so that the rotary cam
16 is rotatably accommodated in the toothed blocks 12A and 12B. The
pair of toothed blocks 12A and 12B are point-symmetrical with
respect to the axis of the pivot 4. As previously described, the
base 1 has the pair of diametrically-opposing curved inner toothed
portions 11a and 11b being formed on the respective curved side
walls 9a and 9b of the recessed portion 10. The inner diameter of
the ring-gear like recessed portion 19 of the arm 2 is identical to
the inner diameter of the diametrically-opposing curved side walls
9a and 9b. Thus, the outer toothed portion 13 of the upper toothed
block 12A are meshable with or unmeshable from both the inner
toothed portion 21a of the arm and the inner toothed portion 11a of
the base to insure an increased mechanical strength of the
reclining device kept in its completely locked state. The operating
lever or the reclining lever 3 is formed with an armed portion 4a
having a spring slot at which one hooked end of a return spring 30
(for example a coiled tension spring) is hanged. The other hooked
end of the return spring 30 is hanged at a bracket 28b of a holder
28 which is fixedly connected to the base 1 by means of rivets or
the like. As a result, the operating lever is biased to its initial
position (a spring-loaded position) by way of the bias of the
spring 30. The holder 28 is also formed integral with a slotted
shaft 28a. The slotted portion of the slotted shaft 28a is engaged
with the innermost central end 31a of a return spring 31 such as a
spiral spring. The outermost curled end 31b of the return spring 31
is engaged with a pin 31c fixed to the arm 2. Thus, the seat back
33 fixedly connected to the arm 2 is permanently forced to tilt
forward (anti-clockwise viewing FIG. 2). The previously-noted
structure of the reclining device is conventional and forms no part
of the present invention.
The rotary-cam type reclining device made according to the
invention is different from a conventional reclining device in that
an arm member employed in the reclining device of the present
invention is formed with a reinforced portion of special geometry,
dimensions and shape which are effective to prevent lack of metal
fill due to elastic deformation or to suppress a so-called "sink
mark" which may occur at the press-worked arm member. The
reinforced portion of the arm will be hereinafter described in
detail by reference to FIGS. 3, 5A and 5B.
As seen in FIGS. 3, 5A and 5B, the arm 2 (2A; 2B) is formed with a
circumferentially-extending stepped portion 22 extending
substantially along the tooth tip circle of the inner toothed
portions 21a and 21b. The stepped portion 22 is formed with a
thin-walled section 23 owing to a sink mark S.sub.2 being formed at
the tooth bottom of the respective inner toothed portions 21a and
21b. Note that the circumferentially-extending stepped portion 22
of the arm 2 is formed integral with a somewhat thick-walled,
reinforced portion 24 (of special geometry, dimensions and shape)
all around the stepped portion 22 on the outside face facing apart
from the inside face having the inner toothed portions 21a and 21b.
As seen in FIG. 5A, the somewhat thick-walled, reinforced portion
24 is a substantially right-angled triangle in radial
cross-section. The substantially right-angled triangle of the
reinforced portion 24 has two straight sides right-angled to each
other and a moderately curved, undulated hypotenuse (like a
compressed S shape) in radial cross-section. The moderately curved
or undulated outside face (moderately curved or undulated
hypotenuse) is composed of a concave curved surface F.sub.1
beginning from a particular position P located outward of the tooth
bottom circle of the inner toothed portions 21a and 21b and
extending toward the stepped portion 22, a concave curved surface
F.sub.3 being in contact with an outer cylindrical surface of the
stepped portion 22, and a convex curved surface F.sub.2 being
continuous between the two concave surfaces F.sub.1 and F.sub.3.
The concave curved surface F.sub.1 corresponds a part of circle of
curvature with a comparatively small radius R.sub.1 and a center of
curvature located in the outside arm section opposite to the inside
arm section with the inner toothed portions 21a and 21b. The convex
curved surface F.sub.2 is curved from the lower end of the concave
curved surface F.sub.1 to a degree that the lower end of the convex
curved surface F.sub.2 is substantially parallel with the side wall
of the thin-walled section 23. The convex curved surface F.sub.2
corresponds to a part of circle of curvature with a comparatively
large radius R.sub.2 greater than the radius R.sub.1 and a center
of curvature located in the inside arm section with the inner
toothed portions 21a and 21b. The concave curved surface F.sub.3 is
curved from the lower end of the convex curved surface F.sub.2 to a
degree that the lower end of the concave curved surface F.sub.3
comes into contact with the outer cylindrical surface of the
stepped portion 22. The concave curved surface F.sub.3 corresponds
to a part of circle of curvature with a medium radius R.sub.3
greater than the radius R.sub.1 and less than the radius R.sub.2
and a center of curvature located in the outside arm section
opposite to the inside arm section with the inner toothed portions
21a and 21b. As set forth above, the outside undulated face
(F.sub.1 ; F.sub.2 ; F.sub.3) of the reinforced portion 24 is
formed into a substantially compressed S shape, and additionally
the thickness of the reinforced portion 24, measured in the axial
direction of the pivot shaft 4, is suppressed or reduced to
approximately 1/5 the sum of the thickness of each of the inner
toothed portions 21a and 21b and the thickness of the thin-walled
section 23. Thus, when press-working the pivotal arm member 2, the
lack of fill S.sub.1 at each edge of teeth of the inner toothed
portions 21a (21b), the lack of fill S.sub.2 at each corner of
teeth of the inner toothed portions 21a (21b), and the lack of fill
S.sub.3 at each edge of the cylindrical portion of the stepped
portion 22 are suppressed or reduced adequately, as may be
appreciated from comparison of the sink marks (the lack of fill)
S.sub.1, S.sub.2 and S.sub.3 shown in FIG. 5A with the sink marks
H.sub.1, H.sub.2 and H.sub.3 shown in FIG. 7. In other words, the
reinforced portion 24 of the particular sink-mark suppressive
geometry and shape is very effective to reduce the lack of metal
fill which may occur after press-working. This was assured by the
inventor of the present application. In the shown embodiment,
although the moderately curved hypotenuse of the substantially
right-angled triangle of the reinforced portion 24 is composed of
three curved surfaces, namely F.sub.1, F.sub.2 and F.sub.3, the
hypotenuse may be composed of at least two curved surfaces such as
a concave curved surface and a convex curved surface to provide the
same effect, that is effective suppression of lack of fill, as the
hypotenuse composed of the three curved surfaces. According to the
reclining device of the present invention employing an arm member
formed integral with a reinforced portion 24 of the particular
sink-mark suppressive geometry and shape, since the reinforced
portion 24 is formed all around the circumferentially-extending
stepped portion 22 on the outside face of the arm opposed to the
inside face formed with the inner toothed portions 21a and 21b, the
reinforced portion 24 of the previously-discussed sink-mark
suppressive geometry and shape functions to effectively suppress or
reduce the lack of metal fill (the sink mark) which may occur after
press-working. Additionally, the reinforced portion 24 continuously
formed all around the stepped portion 22, increases the thickness
of the thin-walled section 23 of the stepped portion 22. This
ensures an increased mechanical strength enough to be proof against
repeated shearing force imparted to the arm and to prevent undue
shear fracture which may occur due to fatigue caused by repeated
shearing force imparted to the arm in the direction perpendicular
to both faces of the arm. As seen in FIG. 5B, it is preferable that
the reinforced portion 24 is partly formed with a plurality of
stronger reinforced portions 25. As seen in FIG. 5B, the
cross-section of each of the stronger reinforced portions 25 is
similar to that of a reinforced portion 53 (of an essentially
rectangular equilateral triangle whose base angles are 45 degrees)
formed in an arm member of the prior art device. As best seen in
FIGS. 1 and 2, in the case that the stronger reinforced portions 25
are further provided partly or intermittently in addition to the
circumferentially-extending reinforced portion 24 of the special
geometry, dimensions and shape, the mechanical strength of the arm
may be further increased.
Referring now to FIGS. 6A and 6B, there are shown force components
FA and FB produced owing to clockwise rotation of the arm under a
locked condition of the reclining device. Under the locked
condition in which the outer toothed portions 13 of the toothed
blocks 12A and 12B are in meshed-engagement with the inner toothed
portions 21a and 21b of the pivotable arm 2, when the arm 2 is
loaded clockwise as shown in FIG. 6A, two force components FA and
FB can be created at the two meshing portions between the outer
toothed portions 13 of the toothed blocks 12A and 12B and the
respective inner toothed portions 21a and 21b of the arm 2. In the
case of the lower meshing portion shown in FIG. 6B, the force
component FA acts to inwardly (upwardly) move the associated
toothed block (the lower toothed block 12B), while the force
component FB acts to outwardly expand (downwardly move) the inner
toothed portion 21b of the arm 2. The force component FB (acting to
outwardly move the arm 2) produces a shearing force acting on the
thinned-wall section 23, since the inner toothed portions 21a and
21b are formed on the inner peripheral surface of the ring-like
recessed portion 19 and the thinned-wall section 23 is formed close
to the inner toothed portion. The shearing force caused by the
force component FB acts on the thinned-wall section 23 regardless
of the thinned-wall section 23 ranging within the inner toothed
portions 21a and 21b or another thinned-wall section 23 ranging
within the non-toothed portions defined between the toothed
portions 21a and 21b. In the shown embodiment, since the
thinned-wall section 23 is effectively reinforced throughout the
inner toothed portions 21a and 21b by means of the reinforced
portion 24 of the previously-discussed particular sink-mark
suppressive geometry and shape, the reinforced arm provide a
mechanical strength enough to be proof against the shearing force,
thus preventing undue shear fracture which may occur due to fatigue
caused by the repeated shearing force. In addition to the
above-mentioned shearing force created by the force component FB at
the meshing portion, an additional shearing force, caused by
clockwise rotation of the seat back and acting circumferentially,
is also applied to the thinned-wall section 23 ranging within the
toothed portions 21a and 21b. In the modified reinforced arm
structure of the invention, since the so-called sink-mark
suppressive reinforced portion 24 is partly formed with
circumferentially equi-distant spaced stronger reinforced portions
25, each having a narrow width as seen in FIGS. 1 and 2. Such
stronger reinforced portions 25 provides a satisfactory mechanical
strength enough to be proof against the circumferentially-acting
shearing force caused by the clockwise rotation of the seat
back.
As will be appreciated from the above, the use of the
previously-explained particular sink-mark suppressive geometry and
shape composed of the plural curved surfaces or portions F.sub.1,
F.sub.2 and F.sub.3, can ensure an adequate mechanical strength or
high durability against the repeated shearing force, while
effectively suppressing the undue sink-mark or lack of fill after
press-working such as cold-forging.
The reclining device of the embodiment operates as follows.
As shown in FIG. 1, suppose that the pivot shafts 4A and 4B are
biased counterclockwise by way of the bias of the return spring 30
and thus engaged with the respective holders 28. Under this
condition, the rotary cam is rotated in the anti-clockwise
direction so that the cam portions 16a, 16b and 16d of the rotary
cam 16 abut the respective cam-connection portions 14a, 14b and 14d
of the cam-contour surface 14. The toothed blocks 12A and 12B slide
radially outward, while being guided by the guiding side walls 9a
and 9b of the recessed portion 10 of the base 1 (1A; 1B). Thus, the
outer toothed portions 13 of the toothed blocks 12A and 12B are
brought into meshed-engagement with the inner toothed portions 21a
and 21b of the pivotal arm 2 (2A; 2B) and the inner toothed
portions 11a and 11b of the base 1 (1A; 1B). In such a case, each
of the reclining devices of the double-sided reclining apparatus is
maintained at the completely locked state in which there is no
relative rotation of the pivotal arms 2A and 2B with respect to the
respective bases 1A and 1B. In such a completely locked state, the
side walls of the toothed blocks 12A and 12B engage with the
respective guiding side walls 9a and 9b of the recessed portion 10
of the base 1 and additionally the outer toothed portions 13 of the
toothed blocks are also in meshed-engagement with the inner toothed
portions 11a and 11b of the recessed portion of the base 1 (1A and
1B). Under these conditions, for example, in the event that the
seat back 33 is excessively loaded by impact force caused by
accidental collision of the vehicle, the impact force is
transmitted through the pivotal arm 2 to the toothed blocks 12A and
12B. The impact load transferred to the respective toothed blocks
12A and 12B is distributed into and received by the guiding side
walls 9a and 9b of the base 1 (1A; 1B) and the inner toothed
portions 11a and 11b of the base. A bearing pressure loaded on the
guiding side walls 9a and 9b can be reduced to approximately half,
thus suppressing undesired deformation of or damage to the guiding
side walls and ensuring a reliable reclining function. For the
purpose of shifting from the previously-noted completely-locked
state to the unlocked state, when the operating lever 3 is pulled
up and rotated clockwise (viewing FIG. 1) against the bias of the
spring 30, the rotary cam 16 also rotates clockwise from its
initial position (the spring-loaded position). The clockwise
rotation of the cam 16 permits the cam portions 16a, 16b and 16d to
be kept out of engagement with the respective cam-connection
portions 14a, 14b and 14d of the cam profile of the cam 14 of each
of the toothed blocks 12A and 12B. Then, the arm 2 becomes rotated
anti-clockwise, since the arm 2 is permanently forced
counter-clockwise by way of the return spring 31. In conjunction
with the clockwise motion of the rotary cam 14, such a rotational
motion of the arm produces an inward sliding motion (or the
contracted motion) of the toothed block pair (12A; 12B). In this
manner, the outer toothed portions (13; 13) of the toothed block
pair are unmeshed from the inner toothed portions 21a and 21b of
the arm 2 and from the inner toothed portions 11a and 11b of the
base 1 by way of the clockwise rotation of the lever 3. Under these
conditions, the seat back 33 can be adjusted toward a desired
inclination angle position. Thereafter, when the lever 3 is
returned again to the initial position with the seat back adjusted
at the desired angular position, the rotary cam 16 also rotates
anti-clockwise together with the lever 3. As a result, the toothed
blocks 12A and 12B become slid outwards, and thus the outer toothed
blocks 12A and 12B are brought again into meshed-engagement with
the inner toothed portions 21a and 21b of the arm and with the
inner toothed portions 11a and 11b of the base. In this manner, the
angular adjustment of the seat back can be attained.
Although the reclining device of the embodiment is exemplified in
case of a diametrically-opposing two toothed blocks (12A; 12B) in
cam-connection with a rotary cam, the device according to the
invention may be applied to a rotary-cam type reclining device with
three or more toothed blocks provided between a rotary cam and
inner toothed portions of a rotatable arm, as disclosed in the
Japanese Patent Provisional Publication No. 6-125821 (corresponding
to French Patent Application No. 91 02590 filed on Mar. 5, 1991).
In the shown embodiment, each of a plurality of stronger reinforced
portions 25 is partly formed as a press-worked reinforcement of an
essentially rectangular equilateral triangle whose base angles are
45 degrees. In lieu thereof, for the purpose of balancing two
contradictory requirements, reduction of undue sink mark (lack of
fill) and high mechanical strength (high durability), each of the
stronger reinforced portions is a substantially right-angled
equilateral triangle in radial cross-section and the substantially
right-angled equilateral triangle of the reinforced portion has two
straight sides right-angled to each other and a concave curved
hypotenuse, and each of two base angles are less than 45
degrees.
While the foregoing is a description of the preferred embodiments
carried out the invention, it will be understood that the invention
is not limited to the particular embodiments shown and described
herein, but that various changes and modifications may be made
without departing from the scope or spirit of this invention as
defined by the following claims.
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